Results on studies of the temporal and spatial variation of gene expression in human brain tissue (Colantuoni et al., 2011; Kang et al., 2011; Naumova et al., 2013) suggest that genetic effects on neurophysiological systems are likely to show both age-related and regional variability. These studies indicate that changes in gene expression trajectories tend to peak in mid to late adolescence. It was also shown that different functional groups of genes have opposite directions of age-related changes of their expression levels. A study of the developmental trajectories of gene expression in the brains of rodents found systematic regional and functional variation of expression extending over the entire developmental period (Stead et al., 2006).
